Wafer boat handling device, vertical batch furnace and method

ABSTRACT

Wafer boat handling device, configured to be positioned under a process chamber of a vertical batch furnace, and comprising a rotatable table comprising a first and a second wafer boat support surface. Each wafer boat support surface is configured for supporting a wafer boat. The rotatable table is rotatable by an actuator to rotate both the first and the second wafer support surfaces to a load/receive position in which the wafer boat handling device is configured to load a wafer boat vertically from the rotatable table into the process chamber and to receive the wafer boat from the process chamber onto the rotatable table, a cooldown position in which the wafer boat handling device is configured to cool down a wafer boat, and a transfer position for transferring wafers to and/or from the wafer boat.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/848,760 filed May 16, 2019 titled WAFER BOAT HANDLINGDEVICE, VERTICAL BATCH FURNACE AND METHOD, the disclosures of which arehereby incorporated by reference in their entirety.

FIELD OF DISCLOSURE

The present disclosure generally relates to a wafer boat handlingdevice. The wafer boat handling device may be configured to bepositioned under a process chamber of a vertical batch furnace. Thepresent disclosure furthermore relates to a vertical batch furnaceassembly comprising said wafer boat handling device. The presentdisclosure also relates to a method for handling wafer boats.

BACKGROUND

Wafer boat handling devices may be positioned under a process chamber ofa vertical batch furnace. Wafer boat handling devices may be part of avertical batch furnace and may be configured to vertically transport awafer boat to a process chamber of said batch furnace, and to receivethe wafer boat from the process chamber. The wafer boat received fromthe vertical batch furnace may be hot and may be cooled down before theprocessed wafers can be taken out of the wafer boat. The wafer boathandling device may be used to transfer wafers to and from the device,in particular to and from the wafer boats accommodated therein. Some ofthe functions of the wafer boat handling devices may be effected by awafer boat carousel which transports the wafer boats.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form. These concepts are described in further detail in thedetailed description of example embodiments of the disclosure below.This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used tolimit the scope of the claimed subject matter.

It may be an object to provide an improved wafer boat handling device.

To that end, the present disclosure provides a wafer boat handlingdevice according to claim 1. More particularly, the wafer boat handlingdevice may be configured to be positioned under a process chamber of avertical batch furnace. The wafer boat handling device comprises arotatable table having just a first and a second wafer boat supportsurface. Each wafer boat support surface may be configured to support awafer boat. The rotatable table may be rotatable around a centralsubstantially vertical axis and may be rotatable by an actuator torotate both the first and the second wafer support surfaces to aload/receive position, a cooldown position, and a transfer position. Inthe load/receive position the wafer boat handling device may beconfigured to load a wafer boat vertically from the rotatable table intothe process chamber and to receive the wafer boat from the processchamber onto the rotatable table. In the cooldown position the waferboat handling device may be configured to cool down a wafer boat. In thetransfer position the wafer boat handling device may be configured toallow wafers to be transferred to and/or from the wafer boat.

The time needed for processing, cooling and transferring may not beequal. When the cooling down is quick, and the transferring is doneefficiently, both actions can be performed within the time needed forprocessing the wafers in the process chamber. The wafer boat handlingdevice therefore may comprise just two wafer boat support surfaces whichcan be transferred to three rotational positions, in particular theload/receive position, the cooldown position, and the transfer position.

An advantage of having only two wafer boat support surfaces is that therotatable table can be made smaller compared to having three wafer boatsupport surfaces. With the three rotational positions in which eachwafer boat support surface can be brought, the wafer boat cooldowndevice can perform the required functions of loading/receiving, coolingdown and transferring while the diameter of the wafer boat handlingdevice may be reduced relative to the known wafer boat handling deviceshaving three wafer boat support surfaces on the rotatable table.Additionally, the costs of manufacturing the wafer boat handling devicemay be smaller than the costs of the wafer boat handling devices withthree wafer boat support surfaces.

The present disclosure also relates to a vertical batch furnace assemblyaccording to claim 13. More particularly, the vertical batch furnaceassembly comprises a process chamber for processing wafers accommodatedin a wafer boat, and a wafer boat handling device according to thepresent disclosure. The wafer boat handling device may be positionedunder the process chamber, and may comprise a wafer boat lift assemblyconfigured to transfer a wafer boat from the wafer boat handling deviceto the process chamber and vice versa.

The vertical batch furnace may have the same advantages as describedabove in relation to the wafer boat handling device.

Further, the present disclosure provides a method for handling waferboats according to claim 15. The method comprises providing a verticalbatch furnace assembly comprising a process chamber and a wafer boathandling device which is positioned under the process chamber, whereinthe wafer boat handling device is the wafer boat handling deviceaccording to the present disclosure. The method further comprisesproviding the first wafer boat support surface with an associated firstwafer boat loaded with wafers and the second wafer boat support surfacewith an associated second wafer boat loaded with wafers, and loading thefirst wafer boat vertically from the first wafer boat support surfacewhich is in the load/receive position into the process chamber. Themethod further comprises processing the wafers accommodated in the firstwafer boat in the process chamber, whilst simultaneously cooling downthe second wafer boat on the second wafer boat support surface which isin the cooldown position, and subsequent to the cooling down, rotate therotatable table to a position in which the second wafer boat supportsurface is in the transfer position. Subsequently, wafers aretransferred to and/or from the second wafer boat, and subsequent to thetransferring, the rotatable table rotates to a position in which thefirst wafer boat support surface is in the load/receive position.

The method may have the same advantages as described above in relationto the wafer boat handing device and the vertical batch furnaceassembly.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught or suggested herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

Various embodiments are claimed in the dependent claims, which will befurther elucidated with reference to an example shown in the figures.The embodiments may be combined or may be applied separate from eachother.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments will becomereadily apparent to those skilled in the art from the following detaileddescription of certain embodiments having reference to the attachedfigures, the invention not being limited to any particular embodiment(s)disclosed.

BRIEF DESCRIPTION OF THE FIGURES

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of theinvention, the advantages of embodiments of the disclosure may be morereadily ascertained from the description of certain examples of theembodiments of the disclosure when read in conjunction with theaccompanying drawings, in which:

FIG. 1 shows a schematic top view of an example of the wafer boathandling device according to the description, wherein the first waferboat is placed on the first wafer boat support surface which is in theload/receive position, and wherein the second wafer boat is placed onthe second wafer boat support surface which is in the cooldown position;

FIG. 2 shows a schematic top view of the example of the wafer boathandling device according to FIG. 1, wherein the first wafer boat isplaced in the process chamber, and wherein the second wafer boat on thesecond wafer boat support surface is in the transfer position;

FIG. 3 shows a perspective view of an example of the vertical batchfurnace assembly;

FIG. 4 shows a schematic top view of the example of the vertical batchfurnace assembly according to FIG. 3; and

FIG. 5 show an example of an arrangement of multiple vertical batchfurnace assemblies of the example according to FIGS. 3 and 4, e.g. in asemi-conductor manufacturing plant.

DETAILED DESCRIPTION OF THE FIGURES

In this application similar or corresponding features are denoted bysimilar or corresponding reference signs. The description of the variousembodiments is not limited to the example shown in the figures and thereference numbers used in the detailed description and the claims arenot intended to limit the description of the embodiments, but areincluded to elucidate the embodiments by referring to the example shownin the figures.

Although certain embodiments and examples are disclosed below, it willbe understood by those in the art that the invention extends beyond thespecifically disclosed embodiments and/or uses of the invention andobvious modifications and equivalents thereof. Thus, it is intended thatthe scope of the invention disclosed should not be limited by theparticular disclosed embodiments described below. The illustrationspresented herein are not meant to be actual views of any particularmaterial, structure, or device, but are merely idealized representationsthat are used to describe embodiments of the disclosure.

As used herein, the term “substrate” or “wafer” may refer to anyunderlying material or materials that may be used, or upon which, adevice, a circuit, or a film may be formed.

FIG. 1 shows a schematic top view of an example of the wafer boathandling device 10, configured to be positioned under a process chamber56 of a vertical batch furnace for processing wafers accommodated in awafer boat 12, 14. The wafer boat handling device 10 comprises arotatable table 16 having just a first and a second wafer boat supportsurface 18, 20. Each wafer boat support surface 18, 20 is configured forsupporting a wafer boat 12, 14. The rotatable table 16 may be rotatableby an actuator around a central substantially vertical axis 22 to rotateboth the first and the second wafer support surfaces 18, 20 to aload/receive position 24, a cooldown position 26, and a transferposition 28.

In the load/receive position 24 the wafer boat handling device 10 may beconfigured to load a wafer boat 12, 14 vertically from the rotatabletable into the process chamber 56 and to receive the wafer boat 12, 14from the process chamber 56 onto the rotatable table 16. In the cooldownposition 26 the wafer boat handling device 10 may be configured to cooldown a wafer boat 12, 14. In the transfer position 28 wafers may betransferred to and/or from the wafer boat 12, 14.

The effects and advantages of the wafer boat handling device 10 havebeen described in the summary section and these effects and advantagesare inserted here by reference.

In an embodiment, of which an example is shown in FIG. 2, the wafer boathandling device 10 may be configured such that the second wafer boatsupport surface 20 of the rotatable table 16 is rotatable by theactuator from the cooldown position 26 to the transfer position 28 whena wafer boat 12, 14 from the first wafer boat support surface 18 hasbeen loaded into the process chamber 56.

With this configuration of the wafer boat handling device 10 it ispossible to have a first wafer boat 12 loaded into the process chamber56, whilst a second wafer boat 14 at the same time can be cooled down inthe cooldown position 26 and subsequently rotated to the transferposition 28 in which transfer position 28 wafers can be transferred toand from the second wafer boat 14. The second wafer boat 14 thereforedoes not have to wait for the first wafer boat 12 to be finished withprocessing before the second wafer boat 14 can be rotated to thetransfer position 28. In this way, even though just two wafer boatsupport surfaces are available, valuable time can be saved because thecooling down of the wafer boat as well as the transferring of wafers inthe cooled down wafer boat can be performed during the processing ofwafers which are accommodated in the other wafer boat which is in theprocess chamber 56. The advantage of a reduced diameter of the waferboat handling device 10 may be combined with a high production capacity.

In an embodiment, a rotational angle of the rotatable table 16 to rotatethe wafer boat support surface 18, 20 from the cooldown position 26 tothe transfer position 28 is enough to prevent heat transfer from a waferboat 12, 14 which is in the cooldown position 26 to a part of acircumferential wall 32 of the wafer boat handling device 10 adjacent tothe transfer position 28 to an extend as to keep the temperature of thepart of the circumferential wall 32 adjacent to the transfer position 28below 70° C., preferably below 50° C.

The circumferential wall 32 adjacent to the transfer position 28 maycomprise a transfer opening 36 and/or a transfer door 38 for wafers topass the circumferential wall 32. When the transfer position 28 would betoo near the cooldown position 26, a hot wafer boat 12, 14 in thecooldown position 26 might have a negative impact on the transfer doorconstruction. In order to withstand the high temperatures of a hot waferboat 12, 14, the design of the transfer door 38 may become very complexand thus expensive. Optionally, the transfer door 38 may be activelycooled such that the wafer boat may be hot when transferred and the boatsubsequently may be cooled down in the transfer position 28. By havingthe rotational angle between the cooldown position 26 and the transferposition 28, the circumferential wall 32 adjacent to the transferposition 28 will not become too hot, which means a more simple transferdoor design is feasible. The rotational angle of the rotatable table 16to rotate the wafer boat support surface 18, 20 from the cooldownposition 26 to the transfer position 28 may be between 1° and 80°,preferably between 40° and 50°, more preferably substantially 45°.

In an embodiment, of which an example is shown in FIG. 1, the wafer boathandling device 10 may be configured such that the second wafer boatsupport surface 20 is in the cooldown position 26 when the first waferboat support surface 18 is in the load/receive position 24. This meansthat the wafer boat handling device 10 can cool down a wafer boat 12, 14in the cooldown position 26, simultaneously to processing a wafer boat12, 14 in the process chamber 56.

A rotational angle of the rotational table 16 to rotate the wafer boatsupport surface 18, 20 from the load/receive position 24 to the cooldownposition 26 may be between 120° and 240°, preferably between 170° and190°, more preferably substantially 180°.

This means that when the first wafer boat support surface 18 is rotatedfrom the load/receive position 24 to the cooldown position 26, thesecond wafer boat support surface 20 is rotated form the cooldownposition 26 to the load/receive position 24. In other words, the waferboat support surfaces 18, 20 swap places, and with them the wafer boats12, 14 on these support surfaces 18, 20.

In an embodiment, the wafer boat handling device 10 is configured tosubsequently:

load a first wafer boat 12 vertically from the first wafer boat supportsurface 18 which is in the load/receive position 24 into the processchamber 56,

cool down a second wafer boat 14 on the second wafer boat supportsurface 20 which is in the cooldown position 26,

rotate the rotatable table 16 to a rotational position in which thesecond wafer boat support surface 20 is in the transfer position 28,

transfer wafers to and/or from the second wafer boat 14, to rotate therotatable table 16 to a rotational position in which the first waferboat support surface 18 is in the load/receive position 24,

receive the first wafer boat 12 from the process chamber 56 on the firstwafer boat support surface 18, and

rotate the rotatable table to a rotational position in which the secondwafer boat support surface 20 is in the load/receive position 24.

Of the three functions of the wafer boat handling device 10, usually theprocessing of the wafers in the process chamber 56 is most timeconsuming. By configuring the wafer boat handling device 10 such thatthe cooling and the transferring are performed within the same time asthe processing, the efficiency of the wafer boat handling device 10 maybe improved. By having the transfer position 28 at a different positionfrom the cooldown position 26 the added advantage is that heat from ahot wafer boat 12, 14 does not raise the temperature of the part ofcircumferential wall 32 adjacent to the transfer position 28 too high.Consequently, a transfer door 38 at the transfer position may have amore simple design, as is explained above in reference to anotherembodiment, which arguments also apply here.

In an embodiment, the wafer boat handling device 10 may further comprisea main housing having a circumferential wall 32 which may be providedwith a transfer opening 36 at the transfer position 28 through whichwafers can be transferred to and from the wafer boat 12, 14 that isaccommodated on the wafer boat support surface 18, 20 which is in thetransfer position 28. The wafer boat handling device 10 may furthercomprise a transfer door 38 configured to open the transfer opening 36when the wafers are transferred, and to close of the transfer opening 36when no wafers are transferred.

In an embodiment, the wafer boat handling device is provided with awafer boat lift assembly having a vertically moveable lift supportmember. The rotatable table 16 may have a lift support opening at boththe first and the second wafer boat support surfaces 18, 20 throughwhich the lift support member can pass the rotatable table 16 foraccommodating the lift support member in a space between a lower side ofthe rotatable table 16 and an upper side of a bottom wall 34 of a mainhousing. The wafer boat lift assembly can transport the wafer boats 12,14 to and from the process chamber 56. The lift support member can passthe rotatable table 16 and lift the wafer boat 12, 14. When the waferboat lift assembly has placed the wafer boat 12, 14 onto the wafer boatsupport surface 18, 20, the lift support member can again pass therotatable table, such that the rotatable table can freely rotate withoutbeing obstructed by said lift support member. The wafer boat liftassembly may be part of the wafer boat handling device 10.

In an embodiment, the wafer boat handling device 10 may further comprisea vertically extending wall structure 46 mounted on the rotatable table16. The vertically extending wall structure 46 may create and at leastpartially bound an associated vertically extending first wafer boatchamber 48 at the first wafer boat support surface 18, and may createand at least partially bound an associated vertically extending secondwafer boat chamber 50 at the second wafer boat support surface 20.

These wafer boat chambers 48, 50 may form mini-environments wherein thewafer boasts 12, 14 are shielded from debris from each other.

In an embodiment, the wafer boat handling device 10 may further comprisea gas circulation system for supplying a gas to and withdrawing the gasfrom at least the first and/or the second wafer boat chamber 48, 50. Thegas circulation system may be configured to cooldown the gas which issupplied to said wafer boat chamber 48, 50. Thus the cooling of thewafer boat 12, 14 in the cooldown position 26 may be effected.

The present disclosure also provides a vertical batch furnace assembly54 comprising a process chamber 56 for processing wafers accommodated ina wafer boat, and a wafer boat handling device 10 according to thepresent disclosure. The wafer boat handling device 10 is positionedunder the process chamber 56, and is provided with a wafer boat liftassembly configured to transfer a wafer boat 12, 14 from the wafer boathandling device 10 to the process chamber 56 and vice versa.

The effects and advantages of the vertical batch furnace assembly havebeen described in the summary section and these effects and advantagesare inserted here by reference.

In an embodiment, of which an example is shown in FIGS. 3 and 4, thevertical batch furnace assembly 54 is provided with a substantiallyrectangular footprint having two opposite short sides 66 defining awidth of the vertical batch furnace assembly and having two oppositelong 68 sides defining a length of the vertical batch furnace assembly.The vertical batch furnace assembly 54 may further comprise at least onecassette in-out port 58, which may be arranged at one of the short sides66 of the vertical batch furnace assembly 54. The vertical batch furnaceassembly preferably comprises two cassette in-out ports 58, which may bearranged adjacent to each other. The vertical batch furnace assembly 54may further comprise a cassette storage 60 configured to store aplurality of substrate cassettes each of which comprises wafers. Thebatch furnace assembly may include a cassette door opener device 70 anda cassette handler 62 which may be configured to transfer substratecassettes between the cassette in-out port 58, the cassette storage 60and the door opener device 70. The cassette storage 60 may be embodiedas a cassette storage carousel. The vertical batch furnace assembly 54may comprise one, or multiple cassette storage carousels, as is shown inFIG. 3. The vertical batch furnace assembly 54 may also comprise a waferhandler 64 configured to transfer wafers between a cassette in the dooropener device 70 and a boat in the wafer boat handling device 10.

By having a substantially rectangular footprint and by having thecassette in-out port 58 arranged at the short side 66 of the verticalbatch furnace, multiple of these vertical batch furnaces 54 can beplaced adjacent to each other, as is shown in FIG. 5. The cassettes withwafers to be processed can be transferred to and from the assembly atthe short side 66 of the vertical batch furnace 54. The other parts ofthe assembly 54 may be arranged in cascade behind the in-out port 58such that the vertical batch furnace assembly 54 may have a certainmaximum width. A width of less than 1.1 m is beneficial in view ofinterchangeability with other vertical batch furnace assemblies.

Finally, the present disclosure provides a method for handling waferboats 10. The method comprises:

providing a vertical batch furnace assembly 54 comprising a processchamber 56 and a wafer boat handling device 10 which is positioned underthe process chamber 56, wherein the wafer boat handling device 10 is thewafer boat handling device 10 according to the present disclosure;

providing the first wafer boat support surface 18 with an associatedfirst wafer boat 12 loaded with wafers and the second wafer boat supportsurface 20 with an associated second wafer boat 14 loaded with wafers;

loading the first wafer boat 12 vertically from the first wafer boatsupport surface 18 which is in the load/receive position 24 into theprocess chamber 56; and

processing the wafers accommodated in the first wafer boat 12 in theprocess chamber 56, whilst simultaneously:

cooling down the second wafer boat 14 on the second wafer boat supportsurface 20 which is in the cooldown position 26;

subsequent to the cooling down, rotate the rotatable table 16 to aposition in which the second wafer boat support surface 20 is in thetransfer position 28;

transferring wafers to and/or from the second wafer boat 14; and

subsequent to the transferring, rotate the rotatable table 16 to aposition in which the first wafer boat support surface 18 is in theload/receive position 24.

The effects and advantages of the method have been described in thesummary section and these effects and advantages are inserted here byreference.

In an embodiment, the method may further comprise:

receiving the first wafer boat 12 from the process chamber 56 on thefirst wafer boat support surface 18; and

subsequently rotate the rotatable table 16 to a rotational position inwhich the second wafer boat support surface 20 is in the load/receiveposition 24.

After these method steps, the wafer boat support surfaces 18, 20 areswapped with respect to the start of the method. That means that themethod herein described can be performed again. By repeating these stepscontinuously, the wafer boat handling device continuously receiveswafers, processes these wafers, cools these wafers and delivers theprocessed wafers.

Although illustrative embodiments of the present invention have beendescribed above, in part with reference to the accompanying drawings, itis to be understood that the invention is not limited to theseembodiments. Variations to the disclosed embodiments can be understoodand effected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, the appearances of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout this description are not necessarily all referring to thesame embodiment.

Furthermore, it is noted that particular features, structures, orcharacteristics of one or more of the various embodiments which aredescribed above may be used implemented independently from one anotherand may be combined in any suitable manner to form new, not explicitlydescribed embodiments. The reference numbers used in the detaileddescription and the claims do not limit the description of theembodiments nor do they limit the claims. The reference numbers aresolely used to clarify.

LEGEND

-   10—wafer boat handling device-   12—first wafer boat-   14—second wafer boat-   16—rotatable table-   18—first wafer boat support surface-   20—second wafer boat support surface-   22—central vertical axis-   24—load/receive position-   26—cooldown position-   28—transfer position-   32—circumferential wall-   34—bottom wall-   36—transfer opening-   38—transfer door-   46—vertically extending wall structure-   48—first wafer boat chamber-   50—second wafer boat chamber-   54—vertical batch furnace assembly-   56—process chamber-   58—cassette in-out port-   60—cassette storage-   62—cassette handler-   64—wafer handler-   66—longitudinal end

The invention claimed is:
 1. A wafer boat handling device, configured tobe positioned under a process chamber of a vertical batch furnace,wherein the wafer boat handling device comprises: a rotatable tablehaving just a first and a second wafer boat support surface, eachconfigured to support a wafer boat configured to accommodate a pluralityof wafers, wherein the rotatable table is rotatable by an actuatoraround a central substantially vertical axis to rotate the first and thesecond wafer support surfaces to: a load/receive position in which thewafer boat handling device is configured to load a wafer boat verticallyfrom the rotatable table into the process chamber and to receive thewafer boat from the process chamber onto the rotatable table; a cooldownposition in which the wafer boat handling device is configured to cooldown a wafer boat; and a transfer position in which the wafer boathandling device is configured to allow transfer of wafers to and/or fromthe wafer boat; and wherein a rotational angle of the rotatable table torotate the wafer boat support surface from the cooldown position to thetransfer position is enough to prevent heat transfer from a wafer boatwhich is in the cooldown position to a part of a circumferential wall ofthe wafer boat handling device adjacent to the transfer position to anextent as to keep the temperature of the part of the circumferentialwall adjacent to the transfer position below 70° C., or below 50° C. 2.The wafer boat handling device according to claim 1, wherein the waferboat handling device is configured such that the second wafer boatsupport surface of the rotatable table is rotatable by the actuator fromthe cooldown position to the transfer position when a wafer boat fromthe first wafer boat support surface has been loaded into the processchamber.
 3. The wafer boat handling device according to claim 1, whereina rotational angle of the rotatable table to rotate the wafer boatsupport surface from the cooldown position to the transfer position isbetween 1° and 80°, or between 40° and 50°, or 45°.
 4. The wafer boathandling device according to claim 1, wherein the wafer boat handlingdevice is configured such that the second wafer boat support surface isin the cooldown position when the first wafer boat support surface is inthe load/receive position.
 5. The wafer boat handling device accordingto claim 4, wherein the wafer handling device is configured with therotational table and the wafer boat support surface being rotatable fromthe load/receive position to the cooldown position over a rotationalangle between 120° and 240°, between 170° and 190°, or 180°.
 6. Thewafer boat handling device according to claim 1, wherein the wafer boathandling device is configured to subsequently: load a first wafer boatvertically from the first wafer boat support surface which is in theload/receive position into the process chamber; cool down a second waferboat on the second wafer boat support surface which is in the cooldownposition; rotate the rotatable table to a rotational position in whichthe second wafer boat support surface is in the transfer position;transfer wafers to and/or from the second wafer boat; rotate therotatable table to a rotational position in which the first wafer boatsupport surface is in the load/receive position; receive the first waferboat from the process chamber on the first wafer boat support surface;and rotate the rotatable table to a rotational position in which thesecond wafer boat support surface is in the load/receive position.
 7. Avertical batch furnace assembly comprising: a process chamber forprocessing wafers accommodated in a wafer boat; a wafer boat handlingdevice according to claim 1, wherein the wafer boat handling device ispositioned under the process chamber.
 8. The vertical batch furnaceassembly according to claim 7, provided with a substantially rectangularfootprint having two opposite short sides defining a width of thevertical batch furnace assembly and having two opposite long sidesdefining a length of the vertical batch furnace assembly, wherein thevertical batch furnace assembly further comprises: at least one cassettein-out port arranged at one of the short sides of the vertical batchfurnace assembly; a cassette storage configured to store a plurality ofsubstrate cassettes each of which comprises wafers; a cassette dooropener device; a cassette handler configured to transfer substratecassettes between the cassette in-out port, the cassette storage and thedoor opener device; a wafer handler configured to transfer wafersbetween a cassette in the door opener device and a boat in the waferboat handling device, wherein the width of the vertical batch furnaceassembly is 1.1 meter or less.
 9. A method for handling wafer boatscomprising: providing a vertical batch furnace assembly comprising aprocess chamber and a wafer boat handling device which is positionedunder the process chamber, wherein the wafer boat handling device is thewafer boat handling device according to claim 1; providing the firstwafer boat support surface with an associated first wafer boat loadedwith wafers and the second wafer boat support surface with an associatedsecond wafer boat loaded with wafers; loading the first wafer boatvertically from the first wafer boat support surface which is in theload/receive position into the process chamber; and processing thewafers accommodated in the first wafer boat in the process chamber,whilst simultaneously: cooling down the second wafer boat on the secondwafer boat support surface which is in the cooldown position; subsequentto the cooling down, rotate the rotatable table to a position in whichthe second wafer boat support surface is in the transfer position;transferring wafers to and/or from the second wafer boat; and subsequentto the transferring, rotate the rotatable table to a position in whichthe first wafer boat support surface is in the load/receive position.10. The method according to claim 9, further comprising receiving thefirst wafer boat from the process chamber on the first wafer boatsupport surface; and subsequently rotate the rotatable table to arotational position in which the second wafer boat support surface is inthe load/receive position.
 11. A wafer boat handling device, configuredto be positioned under a process chamber of a vertical batch furnace,wherein the wafer boat handling device comprises: a rotatable tablehaving just a first and a second wafer boat support surface, eachconfigured to support a wafer boat configured to accommodate a pluralityof wafers, wherein the rotatable table is rotatable by an actuatoraround a central substantially vertical axis to rotate the first and thesecond wafer support surfaces to: a load/receive position in which thewafer boat handling device is configured to load a wafer boat verticallyfrom the rotatable table into the process chamber and to receive thewafer boat from the process chamber onto the rotatable table; a cooldownposition in which the wafer boat handling device is configured to cooldown a wafer boat; and a transfer position in which the wafer boathandling device is configured to allow transfer of wafers to and/or fromthe wafer boat; the wafer boat handling device further comprising a mainhousing having a circumferential wall which is provided with a transferopening at the transfer position through which wafers can be transferredto and from the wafer boat that is accommodated on the wafer boatsupport surface which is in the transfer position.
 12. The wafer boathandling device according to claim 11, further comprising a transferdoor configured to open the transfer opening when the wafers aretransferred, and to close of the transfer opening when no wafers aretransferred.
 13. A vertical batch furnace assembly comprising: a processchamber for processing wafers accommodated in a wafer boat; a wafer boathandling device according to claim 11, wherein the wafer boat handlingdevice is positioned under the process chamber.
 14. A method forhandling wafer boats comprising: providing a vertical batch furnaceassembly comprising a process chamber and a wafer boat handling devicewhich is positioned under the process chamber, wherein the wafer boathandling device is the wafer boat handling device according to claim 11;providing the first wafer boat support surface with an associated firstwafer boat loaded with wafers and the second wafer boat support surfacewith an associated second wafer boat loaded with wafers; loading thefirst wafer boat vertically from the first wafer boat support surfacewhich is in the load/receive position into the process chamber; andprocessing the wafers accommodated in the first wafer boat in theprocess chamber, whilst simultaneously: cooling down the second waferboat on the second wafer boat support surface which is in the cooldownposition; subsequent to the cooling down, rotate the rotatable table toa position in which the second wafer boat support surface is in thetransfer position; transferring wafers to and/or from the second waferboat; and subsequent to the transferring, rotate the rotatable table toa position in which the first wafer boat support surface is in theload/receive position.
 15. A wafer boat handling device, configured tobe positioned under a process chamber of a vertical batch furnace,wherein the wafer boat handling device comprises: a rotatable tablehaving just a first and a second wafer boat support surface, eachconfigured to support a wafer boat configured to accommodate a pluralityof wafers, wherein the rotatable table is rotatable by an actuatoraround a central substantially vertical axis to rotate the first and thesecond wafer support surfaces to: a load/receive position in which thewafer boat handling device is configured to load a wafer boat verticallyfrom the rotatable table into the process chamber and to receive thewafer boat from the process chamber onto the rotatable table; a cooldownposition in which the wafer boat handling device is configured to cooldown a wafer boat; and a transfer position in which the wafer boathandling device is configured to allow transfer of wafers to and/or fromthe wafer boat; the wafer boat handling device further comprising avertically extending wall structure mounted on the rotatable table andcreating and at least partially bounding an associated verticallyextending first wafer boat chamber at the first wafer boat supportsurface, and an associated vertically extending second wafer boatchamber at the second wafer boat support surface.
 16. A vertical batchfurnace assembly comprising: a process chamber for processing wafersaccommodated in a wafer boat; a wafer boat handling device according toclaim 15, wherein the wafer boat handling device is positioned under theprocess chamber.
 17. A method for handling wafer boats comprising:providing a vertical batch furnace assembly comprising a process chamberand a wafer boat handling device which is positioned under the processchamber, wherein the wafer boat handling device is the wafer boathandling device according to claim 15; providing the first wafer boatsupport surface with an associated first wafer boat loaded with wafersand the second wafer boat support surface with an associated secondwafer boat loaded with wafers; loading the first wafer boat verticallyfrom the first wafer boat support surface which is in the load/receiveposition into the process chamber; and processing the wafersaccommodated in the first wafer boat in the process chamber, whilstsimultaneously: cooling down the second wafer boat on the second waferboat support surface which is in the cooldown position; subsequent tothe cooling down, rotate the rotatable table to a position in which thesecond wafer boat support surface is in the transfer position;transferring wafers to and/or from the second wafer boat; and subsequentto the transferring, rotate the rotatable table to a position in whichthe first wafer boat support surface is in the load/receive position.